The present invention relates generally to personnel access apparatuses for enclosures and, more particularly, to a shielded access apparatus for enabling personnel access to an enclosure which is shielded to prevent radiated electromagnetic energy from passing into or out of the enclosure.
It is known that electromagnetic waves can be shielded by an enclosure that is continuously and completely surrounded by an electrically conductive material. Conventional shielded enclosures that employ this concept include either metal components that are continuously welded along all abutting edges or a thin electrically conductive foil applied over the surface of the enclosure to be shielded. Another possible enclosure construction is disclosed in U.S. application Ser. No. 150,286 filed Jan. 29, 1988, which is a continuation of U.S. application Ser. No. 001,225 filed Jan. 6, 1987, now abandoned, by the present inventors and includes an overlapping sheet shielding arrangement which effectively prevents propagation of radiated electromagnetic energy into or out of the enclosure.
Access apparatuses for shielding enclosures have typically included some form of shielded door arrangement. For example, one conventional type of entrance assembly includes two spaced shielded doors and a shielded vestibule extending therebetween. This type of device provides an effective shielding against the propagation of electromagnetic waves when either or both of the shielded doors are closed. This permits personnel to enter or egress the enclosure by passing first through one of the shielded doors, closing that door, and then opening and passing through the second door. As can be appreciated, this type of access device limits the rate of personnel flow into and out of the enclosure. Frequently, this posses no problem. However, where a multiroom or multiple storied enclosure is involved, it would be desirable to provide an access apparatus that both effectively shields radiated energy and permits high flow rates of personnel into and out of the enclosure.
In addition, it would be desirable to provide a shielded access apparatus which permits a high rate of personnel flow but which occupies a reasonable amount of space and which does not require a burdensome effort by personnel passing into or out of the enclosure.
In the above-mentioned prior art apparatuses, as with any entrance apparatus having doors, there exists an occasional expense for maintaining and repairing the doors. This expense can be substantial in apparatuses servicing high numbers of people which are exposed to heavy traffic. It would be desirable to provide a shielded access apparatus that can handle heavy flow rates but which has low maintenance costs as compared to prior art apparatuses servicing flow rates.